A well-deserved congratulations to you! That's very impressive. Our turbine didn't stack up: high 800s on high and mid 600s on low. We think we did very well on the test, but, as you said, it was extraordinarily easy... which I thought was a real shame. We got 18th, which really isn't that bad, but I was disappointed by the test they gave us. We spent a whole year learning all kinds of physics and preparing an extremely comprehensive binder, and we needed neither our physics knowledge nor anything in our binder - it was just about all common sense. We knew our blade setup wasn't going to be the best, so we would need a harder test that we could do well on if we wanted a shot to do well... and that was absolutely not what we got.E Edgar wrote:Here are some results from C-division nationals if anyone is interested.
The test was very easy and so basically the best blades won. The way they had it set up was that there was a high speed fan and a low speed fan. At each fan, they would record your reading for that speed. The fans were not particularly fast and neither were the motors. Of course, that doesn't matter since everyone had the same setup.
Our readings were (these could be slightly off) 1628mV on high and 1287mV on low. We were the very last team to test and were told that our blades were 2nd but very close to Troy's on high power and the fastest in the nation on low power. We took 2nd overall. We got the impression that the 3rd place team was significantly slower but perhaps we were mistaken.
I would also like to say that we got the results we did without any outside design help and so definitely anyone who was motivated enough could have done as well as we did. I molded basswood blades on a metal pipe to get the right curvature. My approach was highly experimental: I changed one variable at a time until I basically got what seemed to be a near-optimal design. Once I had a really good design, I molded several blades to get 2 that were close to identical. In all, I probably molded about 40 pairs of blades to find the design I used and about 10 to get 2 blades that were identical. I learned a huge amount along the way just by observing what worked and by thinking about the physics that determine how the blades function.
One thing: One question I was very confused about was the one about what would happen if the average wind velocity in a wind farm doubled and how would the average available kinetic energy in the air change. I was pretty sure it's Kinetic Energy = 0.5 * rho * area * velocity^3, which means that if the wind speed doubles the kinetic energy should increase by a factor of eight... but the multiple-choice options were 2x, 3x, 4x, 5x, and 6x. We thought that maybe we were missing something and that the word "average" in the problem should trip us off to use rms speed or something, but that didn't make sense either, so we ended up just putting 6x. Did anyone else notice this issue, or am I wrong in the answer I got?
